1. Field of the Invention
This invention relates to safety switches for controlling electric power equipment, such as electric motor driven machinery, and more particularly to power lockout devices to prevent safety switches from being turned to the power on position when the equipment is being serviced.
2. Description of the Related Art
Before working on electric power equipment, such as electric motor driven machinery, it is necessary for safety to lock out the safety switch which controls the electric power fed to the equipment so that the power cannot be turned on and thus risk injury to the worker. Such safety switches are operated by a switch blade handle having a transverse lockout hole which, when the safety switch is off, aligns with a mating lockout hole affixed to the switch box. The worker inserts a padlock into the aligned lockout holes so that the switch cannot be turned on by anyone else.
When a worker wants to work on electrical equipment having many power sources, it is necessary for the worker to lockout each power source with a separate padlock. Thus the worker has to carry a number of padlocks together with a separate key for each lock.
That is especially burdensome for a motor control center having many motor switch boxes. For example, a motor control center can be four feet wide with 10 switches, and even as large as 40 feet wide with 40 switches. And each switch requires its own lockout padlock. Moreover, a number of workers can work on the same equipment with each having the need to lockout the equipment's power sources.
Thus, there was a long felt need for a more efficient way to simultaneously lock out a number of power sources, sometimes by a number of workers, especially for motor control centers with many safety switches.